A majority of the voters (20+40) rank X strictly bottom, so X should be an "irrelevant loser." But with Instant Runoff Voting (IRV), it isn't. IRV elects Y if X does not compete but elects Z if X does compete. This (essentially) actually happened in Louisiana 1991.
There are many other examples, but this is designed to illustrate that this can happen even if a majority of voters rank the loser dead last. E.g.
One can go further by creating artificial elections in which, e.g. H is ranked dead last by 99.9% of the voters, but plays a very important role. (With instant runoff voting: If H runs, then Z wins. If H drops out, then A wins.)
Similar example but for Borda voting
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